Composite polyphase on-load tap-changers for regulating polyphase transformers and polyphase transformers provided with such tap-changers

ABSTRACT

Composite polyphase on-load tap-changer comprising the series connection of at least a rotary polyphase diverter switch adapted to rotate stepwise on and on in both directions and a plurality of monophase tap selectors, said diverter switch having at least one circular series of fixed contacts of which the number is an integer multiple of the number of phases and sets of rotating contacts and rotating transition resistances which are connected to a star point and said tap selectors having each two series of fixed contacts and two alternately moving bridging contacts for connecting each the fixed contacts of a relative series with the same individual fixed contact of the diverter switch.

United States Patent Van Riemsdiik [54] COMPOSITE POLYPI-IASE ON-LOADTAP-CHANGERS FOR REGULATING POLYPHASE TRANSFORMERS AND POLYPHASETRANSFORMERS PROVIDED WITH SUCH TAP- CHANGERS [72] Inventor: GerardusAdriaan Van Riemsdiik, Nijmegen, Netherlands [73] Assignee: SmitNijmegen Electrotechnische Fabrieken N.V., Nijmegen, Netherlands 221Filed: Sept. 23, 1970 [211 Appl No.: 74,631

[51] Int. Cl. ....H02p 13/06, H0lf29/O4 [58] Field of Search ..200/10,11; 323/435 R [56] References Cited UNITEDSTATES PATENTS 3,244,9664/1966 Gertsch et al 323/43 5 R 3,643,154 Feb. 15, 1972 PrimaryExaminer-Gerald Goldberg Attorney-Snyder & Butrum 57 ABSTRACT Compositepolyphase on-load tap-changer comprising the series connection of atleast a rotary polyphase diverter switch adapted to rotate stepwise onand on in both directions and a plurality of monophase tap selectors,said diverter switch having at least one circular series of fixedcontacts of which the number is an integer multiple of the number ofphases and sets of rotating contacts and rotating transition resistanceswhich are connected to a star point and said tap selectors having eachtwo series of fixed-contacts and two alternately moving bridgingcontacts for connecting each the fixed contacts of a relative serieswith the same individual fixed contact of the diverte r switch.

1 Claims, 8 Drawing Figures SHEET 1 OF 2 INVENTOR PATENTEDFEB 15 1972SHEET 2 OF 2 HFIGA HFIGB INVENTOR COMPOSITE POLYPI-IASE ON-LOADTAP-CHANGERS FOR REGULATING POLYPIIASE TRANSFORMERS AND POLYPI-IASETRANSFORMERS PROVIDED WITH SUCH TAP-CHANGERS The invention relates to acomposite polyphase on-load tapchanger for a regulating transformer,said tap-changer consisting of at least two switches connected inseries, of which one switch is a polyphase diverter switch comprising atleast one circular series of angularly equidistanced fixed contacts, ofwhich the number is an integer multiple of the number of phases, atleast one group of mechanically rigidly interconnected equal sets ofrelatively fixed movable contacts, the number of said sets of movablecontacts being equal to the number of phases, said sets of movablecontacts cooperating with said fixed contacts and being mounted forrotation about the axis of said circular series of fixed contacts andsaid sets being equiangularly spaced by angles which are equal to aneven multiple of the angle between the fixed contacts and eachconsisting of one main contact and at least one auxiliary contact, andtransition resistances cooperating with said auxiliary contacts, saidmain and auxiliary contact being relatively mounted and said auxiliarycontacts cooperating with the transition resistances, in such a manner,that during each changeover operation a bridge of resistance is formedbetween the fixed contacts between which thegchangeover operation takesplace, and the other switch is a currentlessly switching polyphase tapselector comprising for each phase two series of pairs fonning fixedcontacts and two alternately movable bridging contacts, of which eachone cooperates with an individual one of said series of fixed contactsfor the interconnection of the fixed contacts of each individual pair ofthe relative series, one contact of each one of said pairs of fixedcontacts being connected with a fixed contact of the diverter switch andthe other contact thereof being intended for connection to a tapping ofa regulating winding of the transformer, said diverter switch beingconnected between said tap selector and a star point.

The invention has for its object to provide a composite onloadtap-changer intended to be connected between the regulating winding ofthe transformer and a star point, in which this disadvantage is avoided,that means in which, irrespective of the number of tappings of thewinding for the fine voltage regulation, the number of fixed contacts ofthe diverter switch need not be greater than an even multiple of thenumber of phases. This means that in a diverter switch for three phasesand single interruption the number of fixed contacts of said diverterswitch need not be greater than six and in a diverter switch for doubleinterruption and three phases this number need not be greater thantwelve. According to the invention this is achieved in that for eachphase all fixed contacts belonging to the same series of the tapselector and connected to the diverter switch are connected both witheach other and with one single individual fixed contact of the or eachcircular series of fixed contacts of the diverter switch. In thistapchanger the tap selector does not operate as phase changeover switchfor the fixed contacts of the diverter switch any more. In the presentcase the changeover of the phases is superfiuous, as during a transitionbetween two transformer tappings not only the connection between saidtappings of each individual phase but also the connection between onetapping of a phase and the other tapping of another phase always takesplace over at least one transition resistance which is inserted betweena tapping and the star point, so that never more than the step voltagecan occur across said resistance and it does not matter, with thetapping of which phase said transition resistance is temporarilyconnected. The on-load tapchanger according to the invention has alsothe advantage that all fixed contacts belonging to a series of the tapselector and connected with the diverter switch may form one continuouscontact path. This makes not only the construction of the tap selectorsimpler but it also means a considerable decrease of the wear and tearof the relative cooperating contacts.

The diverter switch of the tap-changer according to the invention can beconstructed in many ways which will appear from the next description ofthe embodiments of an on-load tap-changer according to the inventionwhich are diagrammatically shown in the drawing.

In the drawing:

FIG. I is a diagrammatical view of a first embodiment of the part,essential to understand the invention, of a composite onload tap-changerfor linear voltage regulation provided with a diverter switch for singleinterruption,

FIG. 2 is a diagrammatical view of an -on-load tap-changer for so-calledplus-and-minus regulation provided with a differently constructeddiverter switch for single interruption,

FIG. 3 is a diagrammatical view of a variant of the diverter switchshown in FIG. 1,

FIG. 4 is a diagrammatical view of a variant of the diverter switchshown in FIG. 2,

FIG. 5 is a diagrammatical view of a composite on-load tapchanger forcoarse and fine regulation provided with a diverter switch for doubleinterruption,

FIG. 6 is a diagrammatical view of a differently constructed diverterswitch for double interruption,

FIG. 7 is a diagrammatical view of a variant of the diverter switchshown in FIG. 5 and FIG. 8 is a diagrammatical view of a variant of thediverter switch shown in FIG. 6.

In FIG. 1 base windings of a threephase transformer are designated by 1.Connected with each one of these windings is a regulating winding 2provided with tapping 3', 3" for the fine voltage steps of theregulating transformer. Cooperating with the regulating windings 2 is athreephase tap selector which comprises for each regulating winding 2fixed contacts 4', 4" connected with the tappings 3, 3" and arranged intwo series, two alternately movable bridging contacts 5, 5" and twofixed contact paths 6', 6". The bridging contacts 5', 5" are adapted toconnect each time a fixed contact 4', 4" with a fixed contact path 6,6".

A threephase diverter switch is designated by 7 and consists of sixequiangularly spaced fixed contacts 8, 9, 10, ll, l2, 13 arranged incircular series, three equiangularly spaced sets of movable contactsmounted for rotation about the axis of said circular series and sixtransition resistances 14.

Each set of movable contacts is composed of a main contact 15 and twoauxiliary contacts 16. The main contacts 15 of the three sets aredirectly connected with a star point 17 and the auxiliary contacts 16are each connected to said star point 17 through a transition resistance14. If, for instance, the sets of mechanically rigidly interconnectedmovable contacts l5, 16 are rotated counterclockwise, the pair ofcontacts 9, 8, the pair of contacts ll, 10 and the pair of contacts 13,12 are each first bridged by two resistances 14 connected in series, sothat in each phase the voltage step occuring between the bridgingcontacts 5', 5" is shunted by said resistances. On further rotation themain contacts 15 are placed on the fixed contacts 8, l0 and 12. In thethen obtained new position of the diverter switch the lowest fixedcontact 4" of each phase is connected with the star point, so that thevoltage supplied by the transformer is equal to the voltage of the basewinding 1 increased by the voltage of one step of the regulating winding2. If a further decrease of the voltage is required the bridging contact5 of each phase must be first shifted to the lowest fixed contact 4 ofthe tap selector. Thereupon the diverter switch must be again rotatedone step counterclockwise. In that case the pair of fixed contacts 8,13, the pair of fixed contacts 10, 9 and the pair of fixed contacts 12,11 are each temporarily bridged by two transition resistances 14connected in series and the contact path 6' of each phase is connectedwith the contact paths 6" of the two other phases.

In the described on-load tap-changer each set of movable contacts of thediverter switch is provided with two auxiliary contacts mounted oneither side of the main contact and two transition resistances which aremoved along with said contacts. Consequently, the diverter switch issymmetrically constructed. Furthermore, the tap selector is onlysuitable for socalled linear voltage regulation, so that the regulatingrange is not greater than that of the regulating winding.

The composite threephase on-load tap-changer shown in FIG. 2 is providedwith a tap selector for so-called plus-andminus regulation and with anasymmetricdiverter switch. To that end the tap selector illustrated inFIG. 1 is amplified with a changeover selector 18, by means of which theregulating winding 2 can be alternately connected with the base winding1 in the same direction and in the opposite direction as the basewinding 1, so that the regulating range is doubled. Furthermore in thistap-changer the diverter switch 19 'is asymmetrically constructed, thatmeans each set of movable contacts has only one auxiliary contact 16 andone transition resistance 14. The asymmetric diverter switch can beadvantageously used in transformers which pass the energy in onedirection only. In that case it is possible to obtain, when theauxiliary contacts 16 are placed on the right side of the main contacts15, that during each changeover operation the circulating currentopposes the main current, so that when the contacts leave a fixedcontact they need to break a smaller power and can be made lighter.Another advantage is that the construction is simpler.

The threephase diverter switch shown in FIG. 3 cooperates withstationary transition resistances 20. To that end said diverter switchis provided with two coaxial circular series of six fixed contacts 21,22, 23, 24, 25, 26 and 27, 28, 29, 30, 31, 32, of which the fixedcontacts 21-26 cooperate with the movable main contacts 33 and the fixedcontacts 27-32 cooperate with the auxiliary contacts 34 which aresymmetrically positioned in regard to the main contacts 33. The sixsymmetrically positioned transition resistances 20 are connectedbetweenthe fixed contact paths 6 and 6" of the three phases of the tap selector(see FIGS. 1 and 2). All movable contacts 33, 34 of this diverter switchare mechanically rigidly interconnected and directly connected with thestar point 17. To the operation of this diverter switch in thetap-changer the same is applicable as to the operation of the diverterswitch in the tap-changer shown in FIG. 1

FIG. 4 shows the asymmetric variant of the diverter switch illustratedin FIG. 3. This diverter switch which operates as the diverter switchshown in FIG. 2 comprises only three auxiliary contacts 34 whichcooperate with the circular series of fixed contacts 27-32.

In FIG. a composite threephase on-load tap-changer is shown, of whichthe tap selector is amplified with a double changeover selector 35, bymeans of which the regulating winding 2 for the fine voltage steps canbe connected either with the end 36 of the base winding 1 or with thefree end 37 of a winding 38 for the coarse voltage regulation which ispermanently connected in series with the base winding. Cooperating withthe contact paths 6, 6" of the tap selector is a diverter switch 39 withdouble interruption which is provided with a circular series of twelvefixed contacts 40, 41,42, 43, 44, 45, 46, 47, 48, 49, 50, 51, with whichthree double sets of movable contacts cooperate. Each double set ofmovable contacts consists of two main contacts 52, 52 directly connectedin series and two pairs of auxiliary contacts 54, 54' positioned oneither side of said main contacts and connected in series throughtransition resistances 53, 53' which are moved together with thecontacts. The resistances 53, 53' connected in series may be replaced byone single resistance. The six fixed contacts 40, 41, 44, 45, 48, 49 areconnected with the contact paths 6', 6" of the three phases of the tapselector and the fixed contacts 42, 43, 46, 47, 50, 51 are connected tothe star point 17. This diverter switch is symmetric and operates withtransition resistances moved along with the contacts.

The asymmetric variant of the diverter switch with double interruptionshown in FIG. 5 is illustrated in FIG. 6. In this diverter switch 55each double set of movable contacts is provided with only onesingle pairof auxiliary contacts 54, 54

connected in series through the transition resistances 53, 53.

In the diverter switch 56, 56' with double interruption shown in FIG. 7the transition resistances 57 are stationary and the three sets ofmovable main contacts 58, 58 which are directly connected in seriescooperate with 12 fixed contacts 59, 60, 61, 62, 63, 64, 65, 66, 67, 68,69, 70 arranged in a first circular series, whereas the sets of doublepairs of auxiliary contacts 71, 71' which are also directly connected inseries cooperate with a second circular series of fixed contacts 72, 73,74, 75, 76, 77, 78, 79, 80, 81, 82, 83. All movable contacts 58, 58',71, 71 are mechanically rigidly interconnected. The fixed contacts 59,60, 63, 64, 67, 68, of the first circular series and the fixed contacts72, 73, 76, 77, 80, 81 of the second circular series are connected withthe contact paths 6, 6" of the tap selector (see FIGS. 1, 2 or 5),whereas the fixed contacts 61, 62, 65, 66, 69, 70 of the first circularseries are directly connected to the star point 17 and the fixedcontacts 74, 75, 78, 79, 82, 83 of the second circular series areconnected to said star point through the transition resistances 57. Thisdiverter switch 56, 56' is symmetrically constructed.

The asymmetric variant of the diverter switch 56, 56 with doubleinterruption shown in FIG. 7 is illustrated in FIG. 8. Therein thediverter switch 84, 84' comprises also two coaxial circular series offixed contacts 59-70 and 72-83, .the first one of which cooperates withthe main contacts 58, 58' and the second one cooperates with only onepair of auxiliary contacts 71, 71' in each phase. Furthermore there areonly three transition resistances 57.

It is observed, that all diverter switches are adapted to cooperate witha tap selector for linear regulation (FIG. 1), a tap selector forplus-and-minus regulation (FIG. 2) or a tap selector for fine-and-coarseregulation (FIG. 5).

What I claim is:

1. Composite polyphase on-load tap-changer for a regulating transformer,said tap-changer consisting of at least two switches connected inseries, of which one switch is a polyphase diverter switch comprising atleast one circular series of angularly equidistanced fixed contacts, ofwhich the number is an integer multiple of the number of phases, atleast one group of mechanically rigidly interconnected equal sets ofrelatively fixed movable contacts, the number of said sets of movablecontacts being equal to the number'of phases, said sets of movablecontacts cooperating with said fixed contacts and being mounted forrotation about the axis of said circular series of fixed contacts andsaid sets being equiangularly spaced by angles which are equal to aneven multiple of the angle between the fixed contacts and eachconsisting of one main contact and at least one auxiliary contact, andtransition resistances cooperating with said auxiliary contacts, saidmain and auxiliary contact being relatively mounted and said auxiliarycontacts cooperating with the transition resistances, in such a manner,that during each changeover operation a bridge of resistance is formedbetween the fixed contacts between which the changeover operation takesplace, and the other switch is a currentlessly switching polyphase tapselector comprising for each phase two series of pairs forming fixedcontacts and two alternately movable bridging contacts, of which eachone cooperates with an individual one of said series of fixed contactsfor the interconnection of the fixed contacts of each individual pair ofthe relative series, one contact of each one of said pairs of fixedcontacts being connected with a fixed contact of the diverter switch andthe other contact thereof being intended for connection to a tapping ofa regulating winding of the transformer, said diverter switch beingconnected between said tap selector and a star point, characterized inthat for each phase all fixed contacts belonging to the same series ofthe tap selector and connected to the diverter switch are connected bothwith each other and with one single individual fixed contact of eachcircular series of fixed contacts of the diverter switch.

1. Composite polyphase on-load tap-changer for a regulating transformer,said tap-changer consisting of at least two switches connected inseries, of which one switch is a polyphase diverter switch comprising atleast one circular series of angularly equidistanced fixed contacts, ofwhich the number is an integer multiple of the number of phases, atleast one group of mechanically rigidly interconnected equal sets ofrelatively fixed movable contacts, the number of said sets of movablecontacts being equal to the number of phases, said sets of movablecontacts cooperating with said fixed contacts and being mounted forrotation about the axis of said circular series of fixed contacts andsaid sets being equiangularly spaced by angles which are equal to aneven multiple of the angle between the fixed contacts and eachconsisting of one main contact and at least one auxiliary contact, andtransition resistances cooperating with said auxiliary contacts, saidmain and auxiliary contact being relatively mounted and said auxiliarycontacts cooperating with the transition resistances, in such a manner,that during each changeover operation a bridge of resistance is formedbetween the fixed contacts between which the changeover operation takesplace, and the other switch is a currentlessly switching polyphase tapselector comprising for each phase two series of pairs forming fixedcontacts and two alternately movable bridging contacts, of which eachone cooperates with an individual one of said series of fixed contactsfor the interconnection of the fixed contacts of each individual pair ofthe relative series, one contact of each one of said pairs of fixedcontacts being connected with a fixed contact of the diverter switch andthe other contact thereof being intended for connection to a tapping ofa regulating winding of the transformer, said diverter switch beingconnected between said tap selector and a star point, characterized inthat for each phase all fixed contacts belonging to the same series ofthe tap selector and connected to the diverter switch are connected bothwith each other and with one single individual fixed contact of eachcircular series of fixed contacts of the diverter switch.